Add code to a paginated report (Report Builder)
Applies to: 
Microsoft Report Builder (SSRS)
Power BI Report Builder
Report Designer in SQL Server Data Tools
In any expression, you can call your own custom code in a paginated report. You can provide code in the following two ways:
Embed code written in Visual Basic directly in your report. If your code refers to a Microsoft .NET Framework that isn't Math or Convert, you must add the reference to the report. For more information, see Add an assembly reference to a report (SSRS). For more information about other references you can make from your code, see Custom code and assembly references in Expressions in Report Designer.
Provide a custom code assembly by using the .NET Framework. If you provide a custom assembly, you must install it on both the computer where you author the report and the report server where you view the report. For more information, see Use custom assemblies with reports.
Add embedded code to a report
In Design view, right-click the design surface outside the border of the report and select Report Properties.
Select Code.
In Custom code, enter the code. Errors in the code produce warnings when the report runs. The following example creates a custom function named
ChangeWordthat replaces the wordBikewithBicycle.Public Function ChangeWord(ByVal s As String) As String Dim strBuilder As New System.Text.StringBuilder(s) If s.Contains("Bike") Then strBuilder.Replace("Bike", "Bicycle") Return strBuilder.ToString() Else : Return s End If End FunctionThe following example shows how to pass a dataset field named Category to this function in an expression:
=Code.ChangeWord(Fields!Category.Value)If you add this expression to a table cell that displays category values, whenever the word
Bikeis in the dataset field for that row, the table cell value displays the wordBicycleinstead.